20643523 has 4 divisors (see below), whose sum is σ = 20658400. Its totient is φ = 20628648.

The previous prime is 20643517. The next prime is 20643527. The reversal of 20643523 is 32534602.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20643523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20643527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5115 + ... + 8212.

It is an arithmetic number, because the mean of its divisors is an integer number (5164600).

Almost surely, 2^20643523 is an apocalyptic number.

20643523 is a deficient number, since it is larger than the sum of its proper divisors (14877).

20643523 is a wasteful number, since it uses less digits than its factorization.

20643523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14876.

The product of its (nonzero) digits is 4320, while the sum is 25.

The square root of 20643523 is about 4543.5143886644. The cubic root of 20643523 is about 274.3224000849.

The spelling of 20643523 in words is "twenty million, six hundred forty-three thousand, five hundred twenty-three".